Neural-Specific Regulation of POMC Gene Expression

描述（由申请人提供） 美国和阿根廷之间的Fogarty国际合作奖的竞争性更新继续支持其母基金P01 DK 55819“摄食和代谢的神经内分泌控制”子项目4“阿片肽对摄食和代谢的调节”中概述的科学目标。“肥胖及其代谢后遗症是全球主要的健康问题。阿片肽β-内啡肽和黑皮质素肽家族都是体重稳态的重要调节剂，也是相同激素原阿黑皮素原（POMC）的产物，其在下丘脑弓状核和脑干孤束核内的特定神经元群体中表达。这两个脑核团都是参与神经内分泌和自主控制食欲和进食的复杂整合的关键区域。POMC基因的突变很少与儿童的早发性病态肥胖和暴食症相关。然而，在几个人群中的遗传研究强烈暗示POMC基因作为肥胖和瘦素水平的数量性状位点。POMC基因编码区的突变会改变肽的产生或功能，但不能解释这种联系，这表明POMC调控序列突变的可能性。关于POMC基因神经特异性表达的分子基础知之甚少，尽管我们假设神经元POMC表达失调可能是能量稳态紊乱的一个促成因素。该FIRCA项目的总体目标是阐明负责大脑中神经元特异性和瘦素调节的POMC基因表达的转录机制，并开发新的分子工具，用于进一步表征POMC肽在食欲和进食控制中的生理特性。这一目标将通过以下具体目标来实现：1）利用转基因小鼠中的缺失和突变分析来鉴定POMC基因中的下丘脑神经特异性增强子（一个或多个）; 2）表征POMC基因中的瘦素反应元件;和3）通过脊椎动物不同目基因组元件的序列比较和POMC基因的分析，转基因小鼠携带红鳍东方鲀的POMC调节序列，红鳍东方鲀是一种硬骨鱼，4.5亿年前从胎盘哺乳动物中分化出来。

DESCRIPTION (provided by applicant) This competitive renewal of a Fogarty International Cooperative Award between the U.S.A. and Argentina is in continued support of the scientific goals outlined in its parent grant P01 DK55819, "Neuroendocrine Control of Feeding and Metabolism," subproject 4, "Modulation of Feeding and Metabolism by Opioid Peptides." Obesity and its metabolic sequelae are major health problems world-wide. The opioid peptide beta-endorphin and a family of melanocortin peptides are both important modulators of weight homeostasis and products of the same prohormone, proopiomelanocortin (POMC), that is expressed in specific populations of neurons within the arcuate nucleus of the hypothalamus and the nucleus tractus solitarius in the brain stem. Both of these brain nuclei are key areas involved in the complex integration of neuroendocrine and autonomic control of appetite and feeding. Null mutations of the POMC gene have rarely been associated with early onset morbid obesity and hyperphagia in children. However, genetic studies in several human populations have strongly implicated the POMC gene as a quantitative trait locus for obesity and leptin levels. Mutations in the coding region of the POMC gene that would alter peptide production or function do not account for this linkage, suggesting the alternative possibility of mutations in POMC regulatory sequences. Little is known about the molecular basis for neural-specific expression of the POMC gene, although we hypothesize that dysregulated neuronal POMC expression may be a contributing factor to disorders of energy homeostasis. The overall goal of this FIRCA project is to elucidate the transcriptional machinery responsible for neuronal-specific and leptin-regulated POMC gene expression in the brain and to develop novel molecular tools for the further physiological characterization of POMC peptides in the control of appetite and feeding. This goal will be addressed by the following specific aims: 1) Identify a hypothalamic neural-specific enhancer(s) in the POMC gene utilizing a deletional and mutational analysis in transgenic mice; 2) Characterize the leptin-responsive element in the POMC gene; and 3) Determine a phylogenetic transcriptional code for the POMC gene by sequence comparisons of genomic elements from divergent orders of vertebrate species and the analysis of transgenic mice carrying POMC regulatory sequences of Fugu rubripes, a teleost fish that diverged from placental mammals 450 million years ago.